1. Field of the Invention
This invention pertains to an implant for directing blood flow directly between a chamber of the heart and a coronary vessel. More particularly, this invention pertains to such an implant with an enhanced design for fixating the implant in a coronary vessel.
2. Description of the Prior Art
U.S. Pat. No. 5,755,682 dated May 26, 1998 and PCT Application No. PCT/US97/13980 (International Publication No. WO 98/06356 based on U.S. patent application Ser. No. 08/882,397 filed Jun. 25, 1997) teach an implant for defining a blood flow conduit directly from a chamber of the heart to a lumen of a coronary vessel. An embodiment disclosed in the aforementioned patent and applications teaches an L-shaped implant in the form of a rigid conduit. The conduit has one leg sized to be received within a lumen of a coronary artery and a second leg sized to pass through the myocardium and extend into the left ventricle of the heart. As disclosed in the above-referenced patent and applications, the conduit is rigid and remains open for blood flow to pass through the conduit during both systole and diastole. The conduit penetrates into the left ventricle in order to prevent tissue growth and occlusions over an opening of the conduit.
Commonly assigned and co-pending U.S. patent application Ser. No. 08/944,313 filed Oct. 6, 1997, entitled "Transmyocardial Implant" teaches an implant such as that shown in the aforementioned '682 patent with an enhanced fixation structure. The enhanced fixation structure includes a fabric surrounding at least a portion of the conduit to facilitate tissue growth on the exterior of the implant.
Implants such as those shown in the aforementioned applications include a portion to be placed within a coronary vessel and a portion to be placed within the myocardium. When placing a portion of the implant in the coronary vessel, the vessel is axially incised a length sufficient to insert the implant. The implant vessel portion is placed within the vessel.
In a preferred embodiment, the implant is rigid. An artery is flexible. A pulsing and alternating flow of blood through the rigid implant and flexible vessel can result in relative movement between through the implant and vessel. As a result of such movement, a rubbing action may occur with the implant causing cellular and extracellular matrix ("ECM") damage to the vessel. Such damage may stimulate cellular migration and proliferation and ECM changes resulting in a fibrotic and thrombotic response which grows to block the implant or artery. Also, as the artery enlarges due to blood flow, an annular gap may exist around the implant in which stagnant blood may collect and stimulate thrombosis. Also, a smooth titanium implant may slip axially relative to a vessel in which the implant is placed. It is an object of the present invention to provide an implant with a reduced likelihood of such response.